Reductant generation systems and methods

ABSTRACT

A system comprises an engine including a plurality of cylinders. A first intake throttle is positioned upstream of a first set of cylinders of the plurality of cylinders. The first intake throttle provides air at a first flow rate to the first set of cylinders so as to produce a lean air/fuel mixture in the first set of cylinders. A second intake throttle is positioned upstream of a second set of cylinders included in the plurality of cylinders and in parallel of the first intake throttle. The second intake throttle provides air at a second flow rate to the second set of cylinders so as to produce a rich air/fuel mixture in the second set of cylinders.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 14/958,558, filed Dec. 3, 2015, the contents of which areincorporated herein by reference in their entirety.

BACKGROUND

Exhaust aftertreatment systems are used to receive and treat exhaust gasgenerated by IC engines. Exhaust gases produced by IC engines operatingon fuels such as gasoline, diesel, liquefied petroleum gas (LPG),ethanol, natural gas and/or dual fuel variants include NOx gases, carbonmonoxide (CO) and/or unburnt hydrocarbons which have to be neutralizedbefore the exhaust gas is expelled into the environment. Aftertreatmentsystems employed for treating the exhaust gas produced by such ICengines operating under stoichiometric conditions often include athree-way catalyst configured to efficiently decompose NOx gases, CO andunburnt hydrocarbons included in the exhaust gas. However, engines thatoperate lean cannot effectively decompose NOx gases with a three-waycatalyst. A selective catalytic reduction (SCR) device, typically inconjunction with a reductant (e.g., urea-water solution (UWS)) injectionsystem is generally used to efficiently decompose NOx emissions in alean environment.

Three-way catalysts are effective when the engine is operated within anarrow band of air to fuel (air/fuel) ratios near the stoichiometricpoint, such that the exhaust gas composition oscillates between rich(excess fuel) and lean (excess oxygen) conditions. Conversion efficiencyfalls very rapidly when the engine is operated outside of this band.Under lean engine operation, the exhaust gas contains excess oxygen, andthe reduction of NOx is not favored. Under rich conditions, the excessfuel consumes all of the available oxygen prior to the catalyst,resulting in poor reduction of CO and unburned hydrocarbons and theformation of ammonia from NOx. From a fuel efficiency perspective, it isbeneficial to operate the engine under lean conditions to minimize fuelconsumption and maximize fuel efficiency. However, the limitation posedby the three-way catalyst for operating within the narrow air to fuelratio prevents this from being a feasible option. UWS injection, inconjunction with SCR technology, is used in some lean engineconfigurations. However, UWS SCR technology adds significant cost andcontrol challenges.

SUMMARY

Embodiments described herein relate generally to systems and methods ofoperating IC engines to increase engine fuel efficiency withoutaffecting aftertreatment system performance and, in particular tooperating a first set of cylinders of an IC engine under leanconditions, a second set of cylinders of an IC engine under richconditions and passing exhaust gas produced by the second set ofcylinders through an ammonia generating catalyst.

In a first set of embodiments, a system comprises an engine including aplurality of cylinders. A first intake throttle is positioned upstreamof a first set of cylinders included in the plurality of cylinders. Thefirst intake throttle provides air at a first flow rate into the firstset of cylinders so as to produce a combustible lean air/fuel mixture inthe first set of cylinders included in the plurality of cylinders. Asecond intake throttle is positioned upstream of a second set ofcylinders included in the plurality of cylinders and in parallel of thefirst intake throttle. The second intake throttle provides air at asecond flow rate into the second set of cylinders so as to produce arich air/fuel mixture in the second set of cylinders irrespective of aload on the engine.

In another set of embodiments, a system comprises an engine having aplurality of cylinders including a first set of cylinders configured toburn an air/fuel mixture at a first equivalence ratio. The first set ofcylinders produces an exhaust gas first portion. A second set ofcylinders is configured to burn an air/fuel mixture at a secondequivalence ratio different from the first equivalence ratio. The secondset of cylinders produces an exhaust gas second portion. An ammoniagenerating catalyst is positioned downstream of and in fluidiccommunication with the second set of cylinders. The ammonia generatingcatalyst receives only the exhaust gas second portion and converts NOxgases included in the exhaust gas second portion to ammonia. A selectivecatalytic reduction system is positioned downstream of the plurality ofcylinders. The selective catalytic reduction system receives the exhaustgas first portion and the exhaust gas second portion containing ammoniatherewithin.

In yet another set of embodiments, a method of operating an engineincluding a plurality of cylinders comprises providing a lean air/fuelmixture to a first set of cylinders of the plurality of cylinders. Thefirst set of cylinders are operated at a first compression ratio. A richair/fuel mixture is provided to a second set of cylinders of theplurality of cylinders. The second set of cylinders are operated at asecond compression ratio different from the first compression ratio. Anexhaust gas second portion produced by the second set of cylinders iscommunicated through an ammonia generating catalyst of an aftertreatmentsystem. The exhaust gas second portion is communicated through at leastone downstream aftertreatment component of the aftertreatment system. Anexhaust gas first portion produced by the first set of cylinders iscommunicated through the at least one downstream aftertreatmentcomponent such that the exhaust gas first portion bypasses the ammoniagenerating catalyst.

In still another set of embodiments, a system comprises an engineincluding a plurality of cylinders. A first intake throttle ispositioned upstream of the first set of cylinders of the plurality ofcylinders. A second intake throttle is positioned upstream of a secondset of cylinders included in the plurality of cylinders. An ammoniagenerating catalyst is positioned downstream of the second set ofcylinders. A controller is communicatively coupled to each of the firstintake throttle and the second intake throttle. The controller includesa first intake throttle circuitry configured to instruct the firstintake throttle to provide air at a first flow rate into the first setof cylinders. The first air flow rate produces a lean air/fuel mixturein the first set of cylinders. A second intake throttle circuitry isconfigured to instruct the second intake throttle to provide air at asecond flow rate into the second set of cylinders. The second flow rateproduces a rich air/fuel mixture in the second set of cylinders. Anammonia determining circuitry is configured to determine the molar flowrate of ammonia produced by the ammonia generating catalyst. A NOxdetermining circuitry is configured to determine the NOx molar flow rateproduced by the first set of cylinders. Furthermore, a NOx/ammonia ratiocontrolling circuitry is configured to control the NOx molar flow ratein the first set of cylinders and ammonia molar flow rate in the secondset of cylinders such that the ratio of NOx to ammonia is 1.

It should be appreciated that all combinations of the foregoing conceptsand additional concepts discussed in greater detail below (provided suchconcepts are not mutually inconsistent) are contemplated as being partof the inventive subject matter disclosed herein. In particular, allcombinations of claimed subject matter appearing at the end of thisdisclosure are contemplated as being part of the inventive subjectmatter disclosed herein.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several implementations in accordance withthe disclosure and are therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

FIG. 1 is a schematic illustration of a system including an IC enginefluidly coupled to an aftertreatment system, according to an embodiment.

FIG. 2 is a schematic block diagram of one embodiment of a controlcircuitry that includes a controller which can be included in the systemof FIG. 1.

FIG. 3 is a schematic illustration of another embodiment of a systemthat includes an IC engine fluidly coupled to an aftertreatment systemincluding various aftertreatment components.

FIG. 4 is a schematic illustration of yet another embodiment of a systemincluding an IC engine fluidly coupled to an aftertreatment system.

FIG. 5 is a schematic illustration of still another embodiment of asystem including an IC engine fluidly coupled to an aftertreatmentsystem.

FIG. 6 is a schematic flow diagram of an embodiment of a method foroperating a plurality of cylinders of an IC engine.

FIG. 7 is a schematic block diagram of a computing device which can beused as the controller of FIG. 1 and/or FIG. 2.

Reference is made to the accompanying drawings throughout the followingdetailed description. In the drawings, similar symbols typicallyidentify similar components, unless context dictates otherwise. Theillustrative implementations described in the detailed description,drawings, and claims are not meant to be limiting. Other implementationsmay be utilized, and other changes may be made, without departing fromthe spirit or scope of the subject matter presented here. It will bereadily understood that the aspects of the present disclosure, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, and designed in a wide variety ofdifferent configurations, all of which are explicitly contemplated andmade part of this disclosure.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

Embodiments described herein relate generally to systems and methods ofoperating IC engines to increase engine fuel efficiency withoutaffecting aftertreatment system performance and, in particular tooperating a first set of cylinders of an IC engine under leanconditions, a second set of cylinders of an IC engine under richconditions and passing exhaust gas produced by the second set ofcylinders through an ammonia generating catalyst.

As described herein, the term “lean air/fuel mixture” refers to anair/fuel mixture having a fuel/air equivalence ratio (φ) of less than1.0. Similarly, the term “rich air/fuel mixture” refers to an air/fuelmixture having a fuel/air equivalence ratio of higher than 1.0.

As described herein, the term “combustion phasing” refers to thelocation of combustion relative to the piston at top dead center (TDC),typically measured by crank angle degrees (CAD). A change in combustionphasing causes a change in the location of the piston during the maximumapparent heat release rate, which directly impacts the peak temperaturesduring combustion.

Operating IC engines, typically run under stoichiometric conditions,such as gasoline engines, ethanol engines, LPG engines or natural gasengines under lean conditions is beneficial as it improves fuelefficiency extending operating range of engines, for example a range ofa vehicle including the engine. Lean operation also allows increasingthe compression ratio of engine cylinders due to improved resistance toauto-ignition. The increased compression ratio improves combustionstability and increases brake thermal efficiency. However, the three-waycatalyst generally used in the aftertreatment system associated withsuch engines cannot efficiently decompose NOx gases included in theexhaust gas at the higher amount of oxygen included in the exhaust gasemitted by engines running on lean air/fuel mixture.

Various embodiments of the systems and methods of operating a first setof cylinders of an engine on a lean air/fuel mixture and a second set ofcylinders of the engine on a rich air/fuel mixture may provide benefitsincluding, for example (1) operating the first set of cylinders underlean conditions at all times even, at high engine loads, therebyallowing higher engine efficiency and higher compression ratio due togreater resistance to auto-ignition; (2) increasing engine efficiencyand increasing operating range; (3) allowing lower combustiontemperatures and heat transfer; (4) generating a reductant in situ viaan ammonia generating catalyst receiving a portion of an exhaust gasfrom a second set of cylinders operating under rich conditions; (5)increasing the average ratio of specific heats of the first set ofcylinders allowing more work to be extracted during expansion; (6)reducing pumping losses of the first set of cylinders at part loadoperation in engines; (7) allowing operating of the second set ofcylinders at rich conditions irrespective of the load on the engine; and(8) providing a proportional ratio of ammonia to NOx gases therebymaintaining efficiency of the aftertreatment system for decomposing NOxgases included in the portion of the exhaust gas produced by the firstset of cylinders.

FIG. 1 is a schematic illustration of a system 100 that includes an ICengine 110 fluidly coupled to an aftertreatment system 150 andoptionally, a controller 170. The IC engine 110 has an engine cylinderblock 112 including a plurality of cylinders that include a firstcylinder 114 a, a second cylinder 114 b, a third cylinder 114 c(collectively referred to herein as “the first set of cylinders 114”)and a fourth cylinder 118. The system 100 includes a first intakethrottle 104, a second intake throttle 109. The aftertreatment system150 includes a SCR system 152 and optionally an oxidation catalyst 160.Each of the plurality of cylinders include a piston (not shown) tocompress an air fuel mixture inserted therein to a predeterminedcompression ratio, as described herein.

An intake manifold 107 is positioned upstream of the first set ofcylinders 114. The intake manifold 107 defines an inlet 102 forreceiving intake air communicated into the intake manifold 107. Invarious embodiments, an intercooler (e.g., the intercooler 242 includedin the system 200 of FIG. 3) can be positioned upstream of the inlet 102and configured to reduce a temperature of the intake air, for example toreduce knocking or auto-ignition. The intake manifold 107 divides into aplurality of inlet conduits. The inlet conduits include a first inletconduit 106 a, a second inlet conduit 106 b and a third inlet conduit106 c (collectively referred to herein as “the first set of inletconduits 106”) which serve the first cylinder 114 a, the second cylinder114 b and the third cylinder 114 c. A fourth inlet conduit 108 servesthe fourth cylinder 118. The fourth inlet conduit 108 is separate fromthe inlet 102 and the manifold 107 and positioned in parallel to theinlet 102 and intake manifold 107.

The first intake throttle 104 is positioned upstream of the first set ofcylinders 114. The first intake throttle 104 can include a valve (e.g.,a butterfly valve), variable valve timing, or any other insertionmechanism configured to meter air flow to the cylinders 114. A first setof fuel metering devices 141 are operatively coupled to the first set ofcylinders 114 to insert the fuel therein. Furthermore, a fourth fuelmetering device 144 is operatively coupled to the fourth cylinder 118 toinsert the fuel therein. The first set of fuel metering devices 141 orthe fourth fuel metering device 144 can include a carburetor, a portfuel injector, direction injection fuel injector or any other insertionmechanism configured to meter fuel (e.g. gasoline or an air/fuelmixture) to the first set of cylinders 114 and the fourth cylinder 118.

Moreover, a first set of ignition devices 146 may be operatively coupledto the first set of cylinders 114 and a fourth fuel ignition device 148is operatively coupled to the fourth cylinder 118, and configured toselectively ignite the air/fuel mixture inserted therein. The first setof ignition devices 146 or the fourth fuel ignition device 148 caninclude spark ignition, laser ignition, or various forms of compressionignition to initiate combustion of cylinders 114 and the fourth cylinder118. In various embodiments, a physical ignition device may not bepresent, for example for compression ignition combustion configurations.

More specifically, the first intake throttle 104 meters air such that acombustible mixture can be achieved for ultra-lean part load conditionsfor the first set of cylinders 114. For example, the first intakethrottle provides air at a first flow rate to the first set of cylinders114 so as to produce a lean air/fuel mixture in the first set ofcylinders 114. The air entering at the first flow rate into the firstset of cylinders 114 mixes with the fuel within or upstream of first setof cylinders 114 to produce a lean air/fuel mixture therein. Inparticular embodiments, the lean air/fuel mixture has an equivalenceratio which has an upper limit defined by the reductant that can beproduced in the fourth cylinder 118. Furthermore, the first set ofcylinders 114 are operated at a first compression ratio which can behigher than a second compression ratio of the fourth cylinder 118 (orotherwise a second set of cylinders as described herein). For example,the first compression ratio can be in the range of 12 to 15, and thesecond compression ratio can be in the range of 8 to 11. However, theranges for the first and second compression ratios can vary.

The first intake throttle 104 controls the first flow rate of the airmetered into the first set of cylinders 114 to prevent ultra-lean partload conditions in the first set of cylinders 114 which may result in anincombustible air/fuel mixture. The first set of cylinders 114 areconstantly operated under lean conditions irrespective of the load onthe engine 110.

The second intake throttle 109 is positioned upstream of the fourthcylinder 118 and in parallel of the first intake throttle 104, forexample in the fourth inlet conduit 108 and meters air so that a richair/fuel mixture is provided in fourth cylinder 118 irrespective of aload on the engine 110. For example, the second intake throttle 109provides air at a second flow rate into the fourth cylinder 109 so as toproduce a rich air/fuel mixture in the fourth cylinder 118.

FIG. 1 shows the second intake throttle 109 positioned in parallel withthe first intake throttle 104 but in other embodiments, the secondintake throttle 109 can be positioned downstream of the first intakethrottle 104. In such embodiments, the fourth inlet conduit 108 can befluidly coupled to the intake manifold 107 to receive a portion of theintake air inserted into the intake manifold 107. In variousembodiments, the first intake throttle 104 can be excluded, for exampleif a stratified air/fuel mixture is directly inserted into the first setof cylinders 114. For example the first intake throttle 104 may beeliminated via optimized spray guided direction injection, conventionaldiesel combustion, variable valve lift, or any other combustion systemthat can operate at ultra-lean, unthrottled conditions or mechanismsother than a throttle to meter air into the first set of cylinders 114.

The second intake throttle 109 can also include a valve (e.g., abutterfly valve), variable valve timing, or any other insertionmechanism configured to meter air flow to the cylinder 118. Fuelmetering device 144 can include a carburetor, a port fuel injector, adirect injection fuel injector or any other insertion mechanismconfigured to provide a fuel (e.g., gasoline, diesel, compressed naturalgas (CNG), ethanol, liquid petroleum gas (LPG) or mixtures thereof) oran air/fuel mixture to communicate a predetermined amount of fuel to thefourth cylinder 118.

In some embodiments, the same fuel (e.g., gasoline, diesel, compressednatural gas (CNG), ethanol, liquid petroleum gas (LPG) or mixturesthereof) is provided to the first set of cylinders 114 and the fourthcylinder 118. In other embodiments, the first set of cylinders 114 isprovided with a first fuel (e.g., diesel) and the fourth cylinder 118 isprovided with a second fuel (e.g., gasoline, diesel, compressed naturalgas (CNG), ethanol, liquid petroleum gas (LPG) or mixtures thereof) soas to produce a desired ratio of NOx produced by the first set ofcylinders 114, and ammonia produced by the ammonia generating catalyst122 as described herein (e.g., NOx/ammonia ratio of 1).

More specifically, the second intake throttle 109 provides a second airflow rate into the fourth cylinder 118 so that the fourth cylinder 118has a rich air/fuel mixture, i.e., an air/fuel mixture having a fuel/airequivalence ratio of greater than 1.0. In particular embodiments, therich air/fuel mixture has an equivalence ratio in the range of 1.0 to1.1 (e.g., 1.03). Furthermore, the fourth cylinder 118 is operated at asecond compression ratio different from the first compression ratio, forexample in the range of 8 to 11. This can allow for improved combustionphasing relative to the baseline case, which increases engine out NOxand therefore ammonia that can be produced across the ammonia generatingcatalyst 122. The second intake throttle 109 always provides a richair/fuel mixture to the fourth cylinder 118 so that the fourth cylinder118 is always operated under rich conditions irrespective of the load onthe engine 110. Use of the first intake throttle 104 and the secondintake throttle 109 decouples the mass flow rates of the first set ofcylinders 114 and the fourth cylinder 118 or otherwise the second set ofcylinders.

FIG. 1 shows the engine 110 including four cylinders such that the firstset of cylinders 114 operate under lean conditions, while the remainingfourth cylinder 118 operates under rich conditions. It should beappreciated that the engine 110 can include any number of cylinders, forexample 6, 8, 10, 12 or even more. Any number of cylinders can beconfigured to run on the lean air/fuel mixture and the rich air/fuelmixture. For example, in other embodiments, the system 100 can includesix cylinders. Four cylinders out of the six cylinders can be configuredto operate on the lean air to fuel ratio and comprise the first set ofthe cylinders. A fifth and sixth cylinder can be configured to operateon the rich air/fuel mixture and comprise a second set of cylinders. Insuch embodiments, each of the second set of cylinders can have aseparate and dedicated second intake throttle or a common second intakethrottle. In particular embodiments, the number of cylinders included inthe first set of cylinders which operate on the lean air/fuel mixturecan be higher than the number of cylinders included in the second set ofcylinders operating on the rich air/fuel mixture.

In some embodiments, the engine 110 can include a dual fuel lowtemperature combustion engine. The first set of cylinders 114 operateunder low temperature combustion for high efficiency and low NOx, forexample high efficiency homogenous charge compression ignition (HCCI),gasoline compression ignition (GCI), reactivity controlled compressionignition (RCCI), or premixed charge compression ignition (PCCI). Incontrast, the fourth cylinder 118 or the second set of cylinders operateusing any fuel, for example CNG, gasoline, ethanol or LPG under richconditions for reductant generation. The lower compression ratio of thefourth cylinder 118 relative to the first set of cylinders 114 allowsthe fourth cylinder 118 to optimize combustion phasing which increasescombustion temperatures and increases NOx production.

Furthermore, the different compression ratios of the first set ofcylinders 114 relative to the fourth cylinder 118 allow for improvedefficiency mitigating indicated mean effective pressure (IMEP)imbalance. IMEP imbalance can occur when various cylinders of an engineare operated at difference compression ratios or equivalence ratios.Having the higher first compression ratio of the first set of cylinders114 relative to the second compression of the fourth cylinder 118 allowsnarrow the IMEP imbalance as well as the power density imbalance due tothe inherent equivalence ratio difference.

The first cylinder 114 a, the second cylinder 114 b and the thirdcylinder 114 c collectively produce an exhaust gas first portioncommunicated via a first outlet conduit 126 a, a second outlet conduit126 b and a third outlet conduit 126 c (collectively referred to hereinas “the first set of outlet conduits 126”) to an exhaust manifold 132.The exhaust gas first portion can include NOx gases, CO and/or unburnthydrocarbons. The fourth cylinder 118 (or the second set of cylinders)produces an exhaust gas second portion which is communicated via afourth outlet conduit 128 to the exhaust manifold 132. In variousembodiments, a first oxidation catalyst (not shown) can be positioneddownstream of the first set of cylinders 114 and configured to decomposeconstituents, for example CO and unburnt hydrocarbons included in theexhaust gas first portion. In other embodiments, a first oxidationcatalyst (not shown) can be positioned downstream of the first set ofcylinders 114 and configured to convert NO to NO₂, such that the ratioof NO₂:NO approaches 1.0 which enables “fast” operation of the SCRsystem 152.

Since the first set of cylinders 114 are always operated under leanconditions, the engine 110 has improved resistance to auto-ignition.This enables a higher compression ratio to be used in the first set ofcylinders 114 for knock limited combustion strategies. Furthermore, thefirst oxidation catalyst or the SCR system 152 perform under the samelean operating condition so that enhanced thermal stability forstoichiometric conditions, for example of the SCR catalyst included inthe SCR system 152 is not necessary.

An ammonia generating catalyst 122 or any other reductant generatingcatalyst is positioned downstream of the fourth cylinder 118 (or thesecond set of cylinders) such that the exhaust gas second portion iscommunicated through the ammonia generating catalyst 122. For example,the ammonia generating catalyst 122 can be positioned in the fourthoutlet conduit 128. The ammonia generating catalyst 122 can include athree-way catalyst configured to partially decompose CO (e.g., decomposeCO into carbon dioxide), unburnt hydrocarbons (e.g., partially decomposeunburnt hydrocarbons in carbon dioxide and water) and fully decomposeNOx gases included in the exhaust gas second portion with highselectivity to ammonia.

Because the fourth fluid conduit 128 is fluidly isolated from the firstset of outlet conduits 126, the exhaust gas first portion bypasses theammonia generating catalyst 122. In other words, only the exhaust gassecond portion passes through the ammonia generating catalyst 122 togenerate ammonia while the exhaust gas first portion does not passthrough the ammonia generating catalyst 122 so that the rich exhaust gasin the fourth fluid conduit 128 can convert the engine out NOx toammonia in an overall lean exhaust mixture at the exhaust manifold 132.The exhaust gas first portion and the exhaust gas second portion thatincludes the ammonia which is generated as the exhaust gas secondportion passes through the ammonia generating catalyst 122, combine inthe exhaust manifold 132. In various embodiments, the ratio of an amountof NOx gases included in the exhaust gas first portion and the amount ofammonia in the exhaust gas second portion is 1 or approximately 1 (e.g.,in the range of 0.9 to 1.1). This balanced ratio of the NOx gases of theamount of NOx to the amount of ammonia enables efficient decompositionof the NOx gases included in the exhaust gas by the SCR system 152, asdescribed herein.

The SCR system 152 is fluidly coupled to the exhaust manifold 132downstream of the first set of outlet conduits 126 and the fourth outletconduit 128. The SCR system 152 includes at least one catalystpositioned within an internal volume defined by a housing of the SCRsystem 152. The catalyst is formulated to selectively reduceconstituents of the exhaust gas, for example NOx included in the exhaustgas in the presence of any exhaust reductant. The ammonia included inthe exhaust gas second portion serves as the reductant for the NOx gasesincluded in the exhaust gas first portion, thereby obviating the use ofa separate reductant supply. Furthermore, the balanced ratio (e.g., inthe range of 0.9 to 1.1) of the amount of NOx gases to the amount ofammonia included in the exhaust gas entering the SCR system 152 enhancesthe efficiency of the SCR system 152.

Any suitable catalyst can be used such as, for example, platinum,palladium, rhodium, cerium, iron, manganese, copper, vanadium basedcatalysts (including combinations thereof). The catalyst can be disposedon a suitable substrate such as, for example, a ceramic (e.g.,cordierite) or metallic (e.g., kanthal) monolith core which can, forexample, define a honeycomb structure. A washcoat can also be used as acarrier material for the catalyst. Such washcoat materials can include,for example, aluminum oxide, titanium dioxide, silicon dioxide, anyother suitable washcoat material, or a combination thereof. The exhaustgas can flow over and about the catalyst such that any NOx gasesincluded in the exhaust gas are further reduced in the presence of theammonia to yield an exhaust gas which is substantially free of carbonmonoxide and NOx gases.

Thus, the system 100 allows operation of the first set of cylinders 114constantly on a lean air to fuel ratio regardless of the operatingconditions of the engine 110. Since the first set of cylinders 114 nevercycle to operate on a rich air/fuel mixture, this allows the compressionratio to be raised due to greater resistance to auto-ignition. Thisimproves engine efficiency as well as extends the operating range of theengine 110. Operating the dedicated fourth cylinder 118 (or a second setof cylinders which can be smaller in number than the first set ofcylinders 114) at the rich conditions provides ammonia via the ammoniagenerating catalyst 122 to facilitate reduction of the NOx gasescontributed by the exhaust gas first portion produced by the first setof cylinders 114. The balanced ratio of the amount NOx gases to theamount of ammonia gas (e.g., 1) facilitates efficient reduction of theNOx gases by the SCR system 152 thus allowing the system 100 to meetstrict emission requirements.

The oxidation catalyst 160 (e.g., a second oxidation catalyst) can bepositioned downstream of the SCR system 152. In some embodiments, theoxidation catalyst 160 is configured to decompose CO and/or unburnthydrocarbons included in the exhaust gas, which may have slipped pastthe SCR. In other embodiments, the oxidation catalyst 160 can beconfigured to decompose any residual ammonia included in the exhaust gasafter passing through the SCR system 152 (e.g., include an ammonia slipcatalyst).

The controller 170 can be communicatively coupled to each of the firstintake throttle 104 and the second intake throttle 109, the first set offuel metering devices 141, and the fourth fuel metering device 144, andconfigured to control the operation thereof. In some embodiments, afirst set of fuel ignition devices 146 can be operatively coupled toeach of the first set of cylinders 114 and a fourth fuel ignition device148 is operatively coupled to the fourth cylinder 118 to ignite theair/fuel mixture therein, for example during a compression stroke. Insuch embodiments, the controller 170 can also be communicatively coupledto the fuel ignition devices 146 and 148, to selectively activate thesame for combusting the air/fuel mixture within the first set ofcylinders 114 and the fourth cylinder 118.

The controller 170 is communicatively coupled to each of the firstintake throttle 104 and the second intake throttle 109, the first set offuel metering devices 141 and the fourth fuel metering device 144, thefirst set of fuel ignition devices 146 and the fourth fuel ignitiondevice 148 Furthermore, the controller 170 is also communicativelycoupled to an ammonia sensor 121 and an oxygen sensor 123 positioneddownstream of the fourth cylinder 118, and a NOx sensor 127 positioneddownstream of the first set of cylinders 114.

The controller 170 is configured to instruct the first intake throttle104 to meter the air flow at ultra-lean conditions for improvedcombustion stability to the first set of cylinders 114. In someembodiments the first intake throttle 104 may be excluded if advancedtechnologies such as stratified spray guided direct injection areimplemented to allow stable combustion of ultra-lean mixtures. Forexample, the first intake throttle 104 may be replaced by variable valveactuation or any technology which can meter relative air flow and/orimprove combustion stability at ultra-lean conditions. The first intakethrottle 104 may also be eliminated if combustion strategies that haveinherent stability in ultra-lean conditions (e.g. conventional dieselcombustion) are used.

The controller 170 is configured to receive an output NOx signal fromthe first NOx sensor 127 (e.g., a physical sensor or a virtual NOxsensor) indicative of the amount of NOx, for example a molar flow rateof NOx emanating for the first set of cylinders 114. The output NOxsignal is used to control fuel metering devices 141/144 and/or ignitiondevices 146/148, for example to control outlet NOx levels (e.g., molarNOx flow rate) in the first set of outlet conduits 126.

The controller 170 is also configured to receive an ammonia outputsignal from the ammonia sensor 121 (e.g., a physical sensor or a virtualammonia sensor) and instruct the second intake throttle 109 to meter airflow to the fourth cylinder 118 so as to control the molar ammonia flowrate from the ammonia generating catalyst 122. For example, the ammoniasensor 121 is used as an input to the fuel metering device 144 in thefourth cylinder 118. The fuel metering device 144 and/or fuel ignitiondevice 148 are used in conjunction with intake throttle 109 and anoxygen sensor 123 to produce the optimal combustion phasing, air massflow rate, and air/fuel ratio to attain the requisite NOx to beconverted over the ammonia generating catalyst 122. Furthermore, thecontroller 170 can use an output signal from the oxygen sensor 123 tocontrol the equivalence ratio of the fourth cylinder 118. Moreover, thetorque output for the first set of cylinders 114 is controlled based onfueling requirement to operate under lean conditions and the torqueoutput of the fourth cylinder 118 is controlled based on air flow rateas is typical of stoichiometric engines so as to operate the fourthcylinder 118 under rich conditions.

Furthermore, the controller 170, based on the output NOx signal and theoutput ammonia signal controls relative air mass flow rates through thefirst intake throttle 104 and the second intake throttle 109 such thatthe molar flow rate of ammonia generated across ammonia generatingcatalyst 122 matches the NOx molar flow rate in the first set of outletconduits 126. For example, the controller 170 can control the air flowrate through the first intake throttle 104 and the second intakethrottle 109 so that a ratio of the molar NOx flow rate and the molarammonia flow rate is 1.

In various embodiments, the controller 170 can be included in a controlcircuitry. For example, FIG. 2 is a schematic block diagram of a controlcircuitry 171 that includes the controller 170 according to anembodiment. The controller 170 includes a processor 172, a memory 174 orother computer readable medium, a transceiver 178 and optionally, asensor 176. It should be understood that the controller 170 shows onlyone embodiment of the controller 170 and any other controller capable ofperforming the operations described herein can be used.

The processor 172 can include a microprocessor, programmable logiccontroller (PLC) chip, an ASIC chip, or any other suitable processor.The processor 172 is in communication with the memory 174 and configuredto execute instructions, algorithms, commands or otherwise programsstored in the memory 174.

The memory 174 includes any of the memory and/or storage componentsdiscussed herein. For example, memory 174 may include RAM and/or cacheof processor 172. Memory 174 may also include one or more storagedevices (e.g., hard drives, flash drives, computer readable media, etc.)either local or remote to device controller 170. The memory 174 isconfigured to store look up tables, algorithms or instructions.

For example, the memory 174 includes a first intake throttle circuitry174 a configured to instruct the first intake throttle 104 to provide anair/fuel mixture at a first equivalence ratio to a first set ofcylinders 114 of the plurality of cylinders. The memory 174 alsoincludes a second intake throttle circuitry 174 b configured to instructthe second intake throttle 109 to provide an air fuel mixture at asecond equivalence ratio to the fourth cylinder 118 (or a second set ofcylinders as described herein).

The memory 174 includes a fuel metering circuitry 174 f configured toselectively instruct the fuel metering devices 141/144 to insert thefuel or otherwise an air/fuel mixture into the first set of cylinders114 and the fourth cylinder 118. Furthermore, the memory 174 includes afuel ignition circuitry 174 g to instruct the ignition devices 146/148to selectively ignite the air/fuel mixture within the first set ofcylinders 114 and the fourth cylinder 118.

The memory 174 also includes an ammonia determining circuitry 174 c. Theammonia determining circuitry 174 c is configured to determine the molarflow rate of ammonia produced by the ammonia generating catalyst 122,for example using the output ammonia signal generated by the ammoniasensor 121. Moreover, the memory 174 also includes a NOx determiningcircuitry 174 d configured to determine the molar flow rate of the NOxproduced by the first set of cylinders 114, for example using the outputNOx signal generated by the NOx sensor 127.

The controller includes a NOx/ammonia ratio controlling circuitry 174 econfigured to control the NOx molar flow rate produced by the first setof cylinders 114 and the molar flow rate of the ammonia produced by thefourth cylinder 118 or otherwise the second set of cylinders so that theratio thereof is 1. For example, the NOx/ammonia ratio controllingcircuitry 174 e can interpret an existing ammonia and NOx flow rate. TheNOx/ammonia ratio controlling circuitry 174 e can include look-uptables, algorithms, equations or maps to air flow rates determine theair flow provided by the first intake throttle 104 and the second intakethrottle 109 which corresponds to a ratio of the molar flow rate of NOxto ammonia of 1. The NOx/ammonia ratio controlling circuitry 174 einstructs the first intake throttle circuitry 174 a and the secondintake throttle circuitry 174 b to control the flow rate of air to thefirst set of cylinders 114 and the fourth cylinder 118 accordingly.

The NOx/ammonia ratio controlling circuitry 174 e can also determine afuel insertion timing, amount of fuel to be inserted and/or ignitiontiming for each of the first set of cylinders 114 and the fourthcylinder 118 or otherwise the second set of cylinders which correspondto a ratio of the molar flow rate of NOx to ammonia of 1. For example,the NOx/ammonia ratio controlling circuitry 174 e can instruct the firstmetering circuitry 174 f and the fuel ignition circuitry 174 g tocontrol the fuel flow rate and/or amount and the ignition time of thefirst set of cylinders 114 and the fourth cylinder 118 accordingly.

In some embodiments, the memory 174 also includes an equivalence ratiodetermining circuitry 174 h. The equivalence ratio determining circuitry174 h can be used to determine the first equivalence ratio of the firstset of cylinders 114 and/or second equivalence ratio of the fourthcylinder 118 or otherwise the second set of cylinders, for example usingan oxygen output signal produced by the oxygen sensor 123. TheNOx/ammonia ratio controlling circuitry 174 e can also be configured tocontrol the first equivalence ratio of the first set of cylinders 114 soas to limit the first equivalence ratio to a maximum level in the firstset of cylinders 114. This allows limiting NOx emissions from the firstset of cylinders 114 such that the ammonia produced from the ammoniagenerating catalyst 122 will be able to fully reduce the NOx over theSCR system 152. The pre-determined maximum equivalence ratio may also beused for an engine protection standpoint for knock mitigation.Furthermore, the NOx/ammonia ratio controlling circuitry 174 e can alsobe configured to control the second equivalence ratio of the fourthcylinder 118 to limit the equivalence ratio in a stoichiometric to richrange at all times for the fourth cylinder 118. For example, theNOx/ammonia ratio controlling circuitry 174 e can be configured tointerpret and use an output signal from the oxygen sensor 123 to controlthe equivalence ratio of the fourth cylinder 118.

The controller 170 also includes a transceiver 178 configured togenerate a first activating signal for activating the first intakethrottle 104 and a second activating signal for activating the secondintake throttle 109, fuel metering signals for activating the fuelmetering devices 141/144, and a fuel ignition signal for activating thefuel ignition devices 146/148. The first activation signal, the secondactivation signal, the fuel metering signals and/or the fuel ignitionsignals can include a voltage, a current or any other electrical signalcommunicated to the first intake throttle 104 and the second intakethrottle 109, respectively to perform the activation. In variousembodiments, the controller 170 can also include one of many sensors toreplace the NOx/ammonia ratio determining circuitry 174 e, NOxdetermining circuitry 174 d, and/or ammonia determining circuitry 174 cto provide feedback for intake throttles 104 and 109 in addition to fuelmetering devices 141 and 144 and ignition devices 146 and 148.

Although not shown in FIG. 1, the aftertreatment system 100 can includeother sensors such as, for example, temperature sensors, pressuresensors, and/or any other sensors. The controller 170 may becommunicatively coupled to one or more such sensors to receive andinterpret signals from one or more of these sensors, for example todetermine the NOx molar flow rate in first set of outlet conduits 126and the ammonia generated across ammonia generating catalyst 122.

FIG. 3 is a schematic illustration of another embodiment of a system 200that includes an IC engine 210 fluidly coupled to an aftertreatmentsystem 250. The IC engine 210 has an engine cylinder block 212 includinga plurality of cylinders that include a first cylinder 214 a, a secondcylinder 214 b, a third cylinder 214 c (collectively referred to hereinas “the first set of cylinders 214”) and a fourth cylinder 218. Thesystem 200 includes a first intake throttle 204, a second intakethrottle 209. The aftertreatment system 250 includes an ammoniagenerating catalyst 222, a first oxidation catalyst 230, a SCR system252 and a second oxidation catalyst 260. Each of the plurality ofcylinders include a piston (not shown) to compress an air fuel mixtureinserted therein to a predetermined compression ratio, as describedherein.

An intake manifold 207 is positioned upstream of a first set ofcylinders 214 of the plurality of the cylinders. Intake air is providedthrough an inlet 202 fluidly coupled to the intake manifold 207. Acompressor 244 (e.g., included in a turbocharger subsystem) ispositioned upstream of the intake manifold 207. The compressor 244 isconfigured to compress the intake air and provide pressurized air to theengine 210 which can increase power output. The compressor 244 isoperatively coupled to a turbine 246 (e.g., included in the turbocharger subsystem) positioned within a flow path of an exhaust gasstream produced by the engine 210, as described herein. The exhaust gasflowing through the turbine 246 drives the turbine 246 which in turndrives the compressor 244. An intercooler 242 is positioned upstream ofthe intake manifold 207 and downstream of the compressor 244.Compressing the intake air by the compressor 244 raises the temperatureof the intake air which can lead to knocking or auto-ignition. Theintercooler 242 serves to reduce the temperature of the air beforecommunicating the intake air into the engine 210, for example to reduceknocking or auto-ignition. In various embodiments, the intercooler 242can be excluded from the system 200. Furthermore, the compressor 244 andthe turbine 246 can also be excluded from the aftertreatment system 250.

The intake manifold 207 divides into a plurality of inlet conduits. Theplurality of inlet conduits include a first inlet conduit 206 a, asecond inlet conduit 206 b and a third inlet conduit 206 c (collectivelyreferred to herein as “the first set of inlet conduits 206”) which servethe first cylinder 214 a, the second cylinder 214 b and the thirdcylinder 214 c, respectively. A fourth inlet conduit 208 serves thefourth cylinder 218. The fourth inlet conduit 208 is fluidly coupled tothe inlet upstream of the intake manifold 207 and positioned in parallelthereto.

The first intake throttle 204 is positioned upstream of the first set ofcylinders 214. The first intake throttle 204 can include a valve (e.g.,a butterfly valve), variable valve timing, or any other insertionmechanism configured to meter air flow to the cylinders 214. Fuelmetering to the first set of cylinders 214 is achieved through fuelinsertion devices (e.g., the first set of fuel metering devices 141),for example a carburetor, a port fuel injector, direct injection fuelinjector or any other insertion mechanism configured to provide a fuel(e.g., gasoline) to the first set of cylinders 214. More specifically,the first intake throttle 204 provides air metering to the first set ofcylinders 214, such that a combustible mixture is attainable forultra-lean conditions. In various embodiments, the first intake throttle204 may be eliminated through variable valve actuation or advancedcombustion strategies including stratified spray guided directinjection, high energy ignition systems, or optimized combustion systemsfor lean environments (e.g. conventional diesel combustion). A leanair/fuel mixture is supplied to the first set of cylinders 214 i.e., anair/fuel mixture having a fuel/air equivalence ratio of less than 1.0.In particular embodiments, the lean air/fuel mixture has an equivalenceratio which is equal to or less than the requisite equivalence ratio toproduce a molar NOx flow rate from cylinders 214 equal to the ammoniamolar flow rate from the ammonia generating catalyst 222. Furthermore,the first set of cylinders 214 are operated at a first compression ratiowhich can be higher than that of the fourth cylinder 218 or otherwise asecond set of cylinders.

The first intake throttle 204 meters air such that there is always alean air/fuel mixture to the first set of cylinders 214 and the firstset of cylinders 214 are constantly operated under lean conditionsirrespective of the load on the engine 210. The second intake throttle209 is positioned upstream of the first intake throttle and in parallelthereto. The second intake throttle 209 meters air flow to the fourthcylinder 218 independently of the first set of cylinders 214.

The second intake throttle 209 can also include a valve (e.g., butterflyvalve), variable valve actuation, or any other insertion mechanismconfigured to meter air flow. Fuel metering to the fourth cylinder 218is achieved through fuel insertion devices (e.g., the fourth fuelinsertion device), for example a carburetor, a port fuel injector, adirect injection fuel injector, or any other insertion mechanismconfigured to provide a fuel (e.g., gasoline). More specifically, thesecond intake throttle 209 meters air such that there is always a richmixture to the fourth cylinder 218 i.e., a fuel/air equivalence ratiogreater than 1.0 irrespective of the load in the fourth cylinder 218. Inparticular embodiments, the rich air/fuel mixture has an equivalenceratio in the range of 1.0 to 1.1 (e.g., 1.03). Furthermore, the fourthcylinder 218 is operated at a second compression ratio, less than thatof the first compression ratio to allow optimal combustion phasingwithout knock for maximum NOx production in a rich environment prior tothe ammonia generating catalyst 222. In various embodiments, acontroller (e.g., the controller 170 or control circuitry 171) can becommunicatively coupled to the first intake throttle 204 and/or thesecond intake throttle 209 and configured to control the operationthereof, as described with respect to controller 170 of FIGS. 1 and 2.

The first cylinder 214 a, the second cylinder 214 b and the thirdcylinder 214 c collectively produce an exhaust gas first portioncommunicated via a first outlet conduit 226 a, a second outlet conduit226 b and a third outlet conduit 226 c (collectively referred to hereinas “the first set of outlet conduits 226”) to an exhaust manifold firstleg 225, respectively. The exhaust gas first portion can include a NOxgases, CO and/or unburnt hydrocarbons. A NOx sensor 227, which caninclude a physical NOx sensor or a virtual (e.g., computationaldetermined) NOx sensor, is positioned in the exhaust manifold first leg225 and configured to determine an amount of NOx gases in the exhaustgas first portion. In various embodiments, the first oxidation catalyst230 is positioned within the exhaust manifold first leg 225 downstreamof the first set of cylinders 214 and configured to decomposeconstituents of the exhaust gas first portion, for example CO andunburnt hydrocarbons included in the exhaust gas first portion. Thefirst oxidation catalyst 230 can convert a portion of the NO to NO₂,such that an NO:NO₂ ratio approaching 1 can be generated at the outletof catalyst 230, enabling “fast” SCR operation. The exhaust gas firstportion is then communicated to an exhaust manifold 232.

The fourth cylinder 218 (or the second set of cylinders) produces anexhaust gas second portion which is communicated to a fourth outletconduit 228. An ammonia generating catalyst 222 or any other reductantgenerating catalyst is positioned downstream of the fourth cylinder 218(or the second set of cylinders) such that the exhaust gas secondportion is communicated through the ammonia generating catalyst 222. Theammonia generating catalyst 222 can include a three-way catalystconfigured to partially decompose CO (e.g., decompose CO into carbondioxide), partially decompose unburnt hydrocarbons (e.g., decomposeunburnt hydrocarbons into carbon dioxide and water) and convert NOxgases included in the exhaust gas second portion into ammonia. Theexhaust gas second portion containing the ammonia generated via theammonia generating catalyst 222 is communicated to the intake manifoldvia an exhaust manifold second leg 229. An ammonia sensor 221 (e.g., aphysical or virtual ammonia sensor) and an oxygen sensor 223 arepositioned in the exhaust manifold second leg 229 and configured todetermine an amount of ammonia and oxygen (which can be used e.g., todetermine an equivalence ratio of the fourth cylinder 218) in theexhaust gas second portion, respectively.

Since the exhaust manifold first leg 225 and the exhaust manifold secondleg 229 meet at the exhaust manifold 232, which is positioned downstreamof the ammonia generating catalyst 222, the exhaust gas first portionbypasses the ammonia generating catalyst 222. In other words, only theexhaust gas second portion passes through the ammonia generatingcatalyst 222 to generate ammonia while the exhaust gas first portiondoes not pass through the ammonia generating catalyst 222 so that theNOx gases included in the exhaust gas first portion do not decompose onreaching the exhaust manifold 232.

The exhaust gas first portion and the exhaust gas second portion thatincludes the ammonia generated as the exhaust gas second portion passesthrough the ammonia generating catalyst 222 combine in the exhaustmanifold 232. In various embodiments, the ratio of an amount of NOxgases included in the exhaust gas first portion and the amount ofammonia in the exhaust gas second portion is 1 or approximately 1 (e.g.,in the range of 0.9 to 1.1). This balanced ratio of the amount of NOxgases to the amount of ammonia enables efficient decomposition of theNOx gases included in the exhaust gas by the SCR system 252, asdescribed herein. For example, the controller 170 or any othercontroller described herein can monitor the molar amount of NOx asdetermined by the NOx sensor 227 and a molar amount of ammonia asdetermined by the ammonia sensor 221. The controller 170 can use thisinformation to control activation of the first intake throttle 204, thesecond intake throttle 209, fuel metering devices and/or fuel ignitiondevices to maintain the ratio of an amount of NOx gases included in theexhaust gas first portion and the amount of ammonia in the exhaust gassecond portion to be 1.

The turbine 246 is positioned downstream of the exhaust manifold firstleg 225 and the exhaust manifold second leg 229. The exhaust gas flowingthrough the turbine 246 rotates the turbine 246 to drive the compressor244 for forcing intake air into the intake manifold 207 as describedbefore herein. The SCR system 252 is positioned downstream of theturbine 246. The SCR system 252 includes at least one catalystpositioned within an internal volume defined by a housing of the SCRsystem 252. The SCR system 252 can be substantially similar to the SCRsystem 152 described with respect to the system 100 of FIG. 1 andtherefore, not described in further detail herein.

Thus, the system 200 allows operation of the first set of cylinders 214constantly on a lean air/fuel mixture regardless of the operatingconditions of the engine 210. Since the first set of cylinders 214 nevercycle to operate on a rich air/fuel mixture, this allows the compressionratio to be raised due to greater resistance to auto-ignition. Thisimproves engine efficiency as well as extends the operating range of theengine 210, as described herein with respect to the system 100. Invarious embodiments, operation of first set of cylinders 214 constantlyon the lean air/fuel mixture results in an overall efficiency increaseof the engine of greater than 10%, for example 11%, 12%, 13%, 14%, 15%,16%, 17%, 18%, 19% or 20% inclusive of all ranges and valuestherebetween or even higher.

Operation of the first set of cylinders 214 may include, but is notlimited to conventional diesel combustion, lean burn gasolinecombustion, gasoline compression ignition (GCI), premixed chargecompression ignition (PCCI), reactivity controlled compression ignition(RCCI), homogeneous charge compression ignition (HCCI), or any otherhigh efficiency lean and relatively low NOx combustion strategy. LowerNOx combustion strategies may result in higher overall performance sincethe requisite NOx reduction potential of the rich cylinder 218 isreduced. This may reduce the ratio of rich to lean cylinders.

The fourth cylinder 218 or otherwise the second set of cylinders may beoperated using a different combustion strategy or fuel of the leanstrategy (e.g. gasoline may be run in the rich cylinders whileconventional diesel run in the lean cylinders) relative to the first setof cylinders 214. Fuel used in the rich cylinder 218 may include but notlimited to compressed natural gas, gasoline, ethanol, liquefiedpetroleum gas, or any other fuel and combustion strategy which canresult in a rich exhaust mixture to convert NOx to ammonia across theammonia generating catalyst 222.

The compression ratio of the fourth cylinder is limited by theauto-ignition characteristics of the fuel used. The compression ratio isconfigured such that combustion phasing is optimized to produce highengine out NOx for the fourth cylinder 218 during rich operation so thatmaximum NOx reduction potential of the fourth cylinder 218 may beachieved. A NOx sensor 253 is positioned downstream of the SCR system252 and configured to measure the amount of NOx in the exhaust gasflowing out of the SCR system 252. The second oxidation catalyst 260(e.g., a second oxidation catalyst) is positioned downstream of the SCRsystem 252. In some embodiments, the second oxidation catalyst 260 isconfigured to decompose CO and/or unburnt hydrocarbons included in theexhaust gas. In other embodiments, the second oxidation catalyst 260 isconfigured to decompose any residual ammonia included in the exhaust gasafter passing through the SCR system 252 (e.g., include an ammonia slipcatalyst).

Exhaust gas recirculation may be used in various forms and engineconfigurations such that EGR is introduced for the lean cylinders 214,but not the rich cylinders 218. This method of operation may have slightefficiency impacts for the lean cylinders, but will significantly reducethe engine out NOx of the lean cylinders, enabling extended load rangeand/or lowered ratio of rich to lean cylinders.

For example, FIG. 4 is a schematic illustration of another embodiment ofa system 500 that includes an IC engine 510 fluidly coupled to anaftertreatment system 550. The IC engine 510 has an engine cylinderblock 512 including a plurality of cylinders that include a firstcylinder 514 a, a second cylinder 514 b, a third cylinder 514 c(collectively referred to herein as “the first set of cylinders 514”)and a fourth cylinder 518. The engine 510 and thereby, the first set ofcylinders 514 and the fourth cylinder 518 included therein can besubstantially similar in structure and function to the engine 210 or 110described herein and, therefore not described in further detail herein.

The system 500 includes a first intake throttle 504 and a second intakethrottle 509, which are substantially similar to the first intakethrottle 104/204 and the second intake throttle 109/209 described beforeherein. The aftertreatment system 550 also includes an ammoniagenerating catalyst 522, a first oxidation catalyst 530, a SCR system552 and a second oxidation catalyst 560, which are substantially similarto the ammonia generating catalyst 122/222, the first oxidation catalyst230, the SCR system 152/252 and the second oxidation catalyst 160/260,respectively described before herein. While not shown, in someembodiments, the system 500 can also include an intercooler (e.g., theintercooler 242), a compressor (e.g., the compressor 244) and/or theturbine (e.g., the turbine 246) as shown in the aftertreatment system200 of FIG. 3 described herein.

An intake manifold 507 is positioned upstream of a first set ofcylinders 541 of the plurality of the cylinders. Intake air is providedthrough an inlet 502 fluidly coupled to the intake manifold 507. Theintake manifold 507 divides into a plurality of inlet conduits. Theplurality of inlet conduits include a first inlet conduit 506 a, asecond inlet conduit 506 b and a third inlet conduit 506 c (collectivelyreferred to herein as “the first set of inlet conduits 506”) which servethe first cylinder 514 a, the second cylinder 514 b and the thirdcylinder 514 c, respectively. A fourth inlet conduit 508 serves thefourth cylinder 518. The fourth inlet conduit 508 is fluidly coupled tothe inlet upstream of the intake manifold 507 and positioned parallelthereto.

The first intake throttle 504 is positioned upstream of the first set ofcylinders 514. The second intake throttle 509 is positioned upstream ofthe first intake throttle 504 and in parallel thereto. The second intakethrottle 509 meters air flow to the fourth cylinder 518 independently ofthe first set of cylinders 514. The first cylinder 514 a, the secondcylinder 514 b and the third cylinder 514 c collectively produce anexhaust gas first portion communicated via a first outlet conduit 526 a,a second outlet conduit 526 b and a third outlet conduit 526 c(collectively referred to herein as “the first set of outlet conduits526”) to an exhaust manifold first leg 525, respectively. A NOx sensor527 is operatively coupled to the exhaust manifold first leg 525 tomeasure an amount (e.g., a molar amount of NOx gases) in the exhaust gasfirst portion.

In various embodiments, the first oxidation catalyst 530 is positionedwithin the exhaust manifold first leg 525 downstream of the first set ofcylinders 514. The fourth cylinder 518 (or the second set of cylinders)produces an exhaust gas second portion which is communicated to a fourthoutlet conduit 528. The ammonia generating catalyst 522 or any otherreductant generating catalyst is positioned downstream of the fourthcylinder 518 (or the second set of cylinders) such that the exhaust gassecond portion is communicated through the ammonia generating catalyst522. An ammonia sensor 521 and an oxygen sensor 523 are positioneddownstream of the ammonia generating catalyst 522.

The aftertreatment system 500 also includes an exhaust gas recirculation(EGR) system for recirculating a portion of the exhaust gas firstportion from the exhaust manifold first leg 525 to the intake manifold507. The EGR system includes an EGR conduit 570 fluidly coupling theexhaust manifold first leg 525 to the intake manifold 507. An EGR valve572 is positioned within the EGR conduit 570 and structured to controlthe flow rate of the portion of the exhaust gas first portion from theexhaust manifold first leg 525 to the intake manifold 507. Therecirculated portion of the exhaust gas first portion dilutes the O₂ inthe intake air stream and provides gases inert to combustion to act asabsorbents of combustion heat to reduce peak temperature in first set ofcylinders 514 operating on lean air/fuel mixture.

In some embodiments, an aftertreatment system coupled to an engine canalso include a low pressure and high pressure EGR loop, an intercoolerand/or a turbocharger. For example, FIG. 5 is a schematic illustrationof another embodiment of a system a system 600 that includes an ICengine 610 fluidly coupled to an aftertreatment system 650. The ICengine 610 has an engine cylinder block 612 including a plurality ofcylinders that include a first cylinder 614 a, a second cylinder 614 b,a third cylinder 614 c (collectively referred to herein as “the firstset of cylinders 614”) and a fourth cylinder 618. The engine 610 andthereby, the first set of cylinders 614 and the fourth cylinder 618included therein can be substantially similar in structure and functionto the engine 110/210/510 described herein and, therefore not describedin further detail herein.

The system 600 includes a first intake throttle 604 and a second intakethrottle 609, which are substantially similar to the first intakethrottle 104/204/504 and the second intake throttle 109/209/509described before herein. The aftertreatment system 650 also includes anammonia generating catalyst 622, a first oxidation catalyst 630, a SCRsystem 652 and a second oxidation catalyst 660, which are substantiallysimilar to the ammonia generating catalyst 122/222/522, the firstoxidation catalyst 230/530, the SCR system 152/252/552 and the secondoxidation catalyst 160/260/560 described before herein.

An intake manifold 607 is positioned upstream of a first set ofcylinders 614 of the plurality of the cylinders. Intake air is providedthrough an inlet 602 which divides into a first inlet 605 fluidlycoupled to the intake manifold 607, and a second inlet 603. The intakemanifold 607 divides into a plurality of inlet conduits. The pluralityof inlet conduits include a first inlet conduit 606 a, a second inletconduit 606 b and a third inlet conduit 606 c (collectively referred toherein as “the first set of inlet conduits 606”) which serve the firstcylinder 614 a, the second cylinder 614 b and the third cylinder 614 c,respectively. The first intake throttle 604 is positioned in the intakemanifold 607 and structured to control a first air flow rate into thefirst set of inlet conduits 606 and, thereby the first set of cylinders614.

The second inlet 603 is fluidly coupled to the fourth inlet conduit 608serving the fourth cylinder 618. The fourth inlet conduit 608 is fluidlycoupled to the inlet upstream of the intake manifold 607 and positionedparallel thereto. The second intake throttle 609 is positioned in thefourth inlet conduit 608 and structured to control a second flow rate ofair into the fourth inlet conduit 608 and, thereby the fourth cylinder608.

An intercooler 642 is positioned upstream of the intake manifold 607 andthe fourth inlet conduit 608 and fluidly coupled to the first inlet 605and the second inlet 603. The first intake throttle 604 is positioneddownstream of the intercooler 642, while the second intake throttle 609is positioned upstream of the fourth cylinder 618 and downstream of theintercooler 642. A turbine 646 is positioned in an exhaust manifold 632and operatively coupled to a first compressor 644 operatively coupled tothe first inlet 605 and a second compressor 643 operatively coupled tothe second inlet 603. An exhaust gas first portion from the first set ofcylinders 614 and an exhaust gas second portion from the fourth cylinder618 combine in the exhaust manifold 632 before entering the turbine 646.The combined exhaust gas powers the turbine 646 which operates the firstcompressor 644 and the second compressor 643 to compress the intake airprovided to the first set of cylinders 614 and the fourth cylinder 618,as described herein.

The second intake throttle 609 meters air flow to the fourth cylinder618 independently of the first set of cylinders 614. The first cylinder614 a, the second cylinder 614 b and the third cylinder 614 ccollectively produce an exhaust gas first portion communicated via afirst outlet conduit 626 a, a second outlet conduit 626 b and a thirdoutlet conduit 626 c (collectively referred to herein as “the first setof outlet conduits 626”) to the exhaust manifold first leg 625,respectively. A NOx sensor 627 is operatively coupled to the exhaustmanifold first leg 625 to measure an amount (e.g., a molar amount of NOxgases) in the exhaust gas first portion.

In various embodiments, the first oxidation catalyst 630 is positionedwithin the exhaust manifold first leg 625 downstream of the first set ofcylinders 614. The fourth cylinder 618 (or the second set of cylinders)produces an exhaust gas second portion which is communicated to a fourthoutlet conduit 628. The ammonia generating catalyst 622 or any otherreductant generating catalyst is positioned downstream of the fourthcylinder 618 (or the second set of cylinders) such that the exhaust gassecond portion is communicated through the ammonia generating catalyst622. An ammonia sensor 621 and an oxygen sensor 623 is positioneddownstream of the ammonia generating catalyst 622.

The system 600 also includes EGR system including a high pressure loopand a low pressure loop. The high pressure loop includes a first EGRconduit 670 fluidly coupling the exhaust manifold first leg 625 upstreamof the first oxidation catalyst 630 to the intake manifold 607downstream of the first intake throttle 604, and structured torecirculate a portion of the high pressure exhaust gas first portionfrom the exhaust manifold first leg 625 to the intake manifold. A firstEGR valve 672 is positioned within the first EGR conduit 670 to controlan amount of the portion of the high pressure exhaust gas first portionrecirculated to the intake manifold 607. A high pressure EGR cooler 675is fluidly coupled to the first EGR conduit 670 and is structured tocool the high pressure exhaust gas first portion recirculated to intakemanifold 607.

The low pressure loop includes a second EGR conduit 674 fluidly couplingan exhaust manifold 632 downstream of the turbine 646 and upstream ofthe SCR system 652 to the first inlet 605 upstream of the firstcompressor 644. The second EGR conduit 674 recirculates a portion of theexhaust gas from the exhaust manifold 632, which is at a lower pressurethan the exhaust gas first portion after expansion in the turbine 646,to the first inlet 605. A second EGR valve 676 is positioned within thesecond EGR conduit 674 to control an amount of the portion of the lowpressure exhaust gas recirculated to the first inlet 605. Furthermore, alow pressure EGR cooler 677 is fluidly coupled to the second EGR conduit674 and is structured to cool the portion of the low pressure exhaustgas recirculated to the first inlet 605.

FIG. 6 is a schematic flow diagram of an example method 300 of operatingan engine which includes a plurality of cylinders, for example theengine 110, 210, 510 or 610 as described herein. The engine is fluidlycoupled to an aftertreatment system, for example the aftertreatmentsystem 150, 250, 550 or 650. The operations of the method 300 can bestored in the form of instructions on a non-transitory CRM (e.g., thememory 174 of the controller 170, or main memory 736, read only memory(ROM) 738 or storage device 740 included in the computing device 730 ofFIG. 7). The CRM can be included in a computing device (e.g., thecomputing device 730) which is configured to execute the instructionsstored on the CRM to perform the operations of the method 300.

The method 300 includes providing a lean air/fuel mixture to a first setof cylinders of the plurality of cylinders at 302. For example, thelimited use of intake throttle 104/204/504/604 combined with properfueling strategy provides a lean air/fuel mixture to the first set ofcylinders 114/214/514/614 of the engine 110/210/510/610. In variousembodiments, the lean air/fuel mixture has a pre-determined not toexceed equivalence ratio threshold so that the molar flow rate of NOx ofthe first set of cylinders 114/214/514/614 does not exceed the maximummolar flow rate of ammonia from the second set of cylinders118/218/518/618. The first set of cylinders are operated at a firstcompression ratio at 304 to optimize lean combustion strategies such asconventional diesel, lean burn gasoline, or other high efficiency lowtemperature combustion strategies.

A rich air to fuel ratio is provided to a second set of cylinders of theplurality of cylinders 306. For example, the rich air to fuel ratio isprovided to the fourth cylinder 118/218/518/618 or otherwise a secondset of cylinders as described before herein. In various embodiments, therich air/fuel mixture has a second equivalence ratio configured toproduce a stoichiometric air/fuel mixture if no NOx reduction is neededand adjustable to produce a rich air/fuel mixture such that ammoniaproduction across the catalyst is maximized. The second set of cylindersis operated at a second compression ratio different from the firstcompression ratio at 308. The second compression ratio is limited by thefuel used in the second set of cylinders, so that optimal combustionphasing for NOx production can be achieved without uncontrolledauto-ignition.

An exhaust gas second portion produced by the second set of cylinders iscommunicated through an ammonia generating catalyst of an aftertreatmentsystem at 310. For example, the exhaust gas second portion produced bythe fourth cylinder 118/218/518/618 is communicated through the ammoniagenerating catalyst 122/222/522/622 included in the aftertreatmentsystem 150/250/550/650, respectively as described before herein. Theammonia generating catalyst can include, for example a three-waycatalyst formulated to partially decompose CO and unburnt hydrocarbonsincluded in the exhaust gas second portion, as well as convert NOx gasesinto ammonia, as described before herein.

The exhaust gas second portion is communicated through at least onedownstream component of the aftertreatment system at 312. For example,the exhaust gas second portion is communicated through the SCR system152/252/552/652, and/or the second oxidation catalyst 160/260/560/660included in the aftertreatment system 150/250/550/650, as describedbefore herein. An exhaust gas first portion produced by the first set ofcylinders is also communicated through the at least one downstreamaftertreatment component at 314. The exhaust gas first portion bypassesthe ammonia generating catalyst. For example, the exhaust gas firstportion produced by the first set of cylinders 114/214/514/614 iscommunicated through the first oxidation catalyst 230/530/630 or anexhaust manifold first leg (e.g., the exhaust portion first leg225/525/625) to the exhaust manifold 132/232/532/632 and therefrom tothe downstream SCR system 152/252/552/652, and/or the second oxidationcatalyst 160/260/560/660, as described before herein. A ratio of anamount of NOx gases included in the exhaust gas first portion and anamount of ammonia in the exhaust gas second portion can be 1 orapproximately 1 (e.g. in the range of 0.9 to 1.1). The balanced ratioincreases the efficiency of the SCR system 152/252/552/652 in reducingthe NOx gases included in the exhaust gas second portion facilitated bythe ammonia provided by the exhaust gas second portion which serves asthe reductant.

In some embodiments, the controller 170, the control circuitry 171 orany of the controller or control circuitries described herein cancomprise a system computer of an apparatus or system which includes theaftertreatment system 100 or 200 (e.g., a vehicle, an engine orgenerator set, etc.). For example, FIG. 7 is a block diagram of acomputing device 730 in accordance with an illustrative implementation.The computing device 730 can be used to perform any of the methods orthe processes described herein, for example the method 300. In someembodiments, the controller 170 can include the computing device 730.The computing device 730 includes a bus 732 or other communicationcomponent for communicating information. The computing device 730 canalso include one or more processors 734 or processing circuits coupledto the bus for processing information.

The computing device 730 also includes main memory 736, such as a randomaccess memory (RAM) or other dynamic storage device, coupled to the bus732 for storing information, and instructions to be executed by theprocessor 734. Main memory 736 can also be used for storing positioninformation, temporary variables, or other intermediate informationduring execution of instructions by the processor 734. The computingdevice 730 may further include ROM 738 or other static storage devicecoupled to the bus 732 for storing static information and instructionsfor the processor 734. A storage device 740, such as a solid-statedevice, magnetic disk or optical disk, is coupled to the bus 732 forpersistently storing information and instructions. For example,instructions for determining the first equivalence ratio and the secondequivalence ratio can be stored in the storage device 740.

The computing device 730 may be coupled via the bus 732 to a display735, such as a liquid crystal display, or active matrix display, fordisplaying information to a user. An input device 742, such as akeyboard or alphanumeric pad, may be coupled to the bus 732 forcommunicating information and command selections to the processor 734.In another implementation, the input device 742 has a touch screendisplay 744.

According to various implementations, the processes and methodsdescribed herein can be implemented by the computing device 730 inresponse to the processor 734 executing an arrangement of instructionscontained in main memory 736 (e.g., the operations of the method 300).Such instructions can be read into main memory 736 from anothernon-transitory computer-readable medium, such as the storage device 740.Execution of the arrangement of instructions contained in main memory736 causes the computing device 730 to perform the illustrativeprocesses described herein. One or more processors in a multi-processingarrangement may also be employed to execute the instructions containedin main memory 736. In alternative implementations, hard-wired circuitrymay be used in place of or in combination with software instructions toeffect illustrative implementations. Thus, implementations are notlimited to any specific combination of hardware circuitry and software.

Although an example computing device has been described in FIG. 7,implementations described in this specification can be implemented inother types of digital electronic circuitry, or in computer software,firmware, or hardware, including the structures disclosed in thisspecification and their structural equivalents, or in combinations ofone or more of them.

Implementations described in this specification can be implemented indigital electronic circuitry, or in computer software, firmware, orhardware, including the structures disclosed in this specification andtheir structural equivalents, or in combinations of one or more of them.The implementations described in this specification can be implementedas one or more computer programs, i.e., one or more modules of computerprogram instructions, encoded on one or more computer storage media forexecution by, or to control the operation of, data processing apparatus.Alternatively or in addition, the program instructions can be encoded onan artificially-generated propagated signal, e.g., a machine-generatedelectrical, optical, or electromagnetic signal that is generated toencode information for transmission to suitable receiver apparatus forexecution by a data processing apparatus. A computer storage medium canbe, or be included in, a computer-readable storage device, acomputer-readable storage substrate, a random or serial access memoryarray or device, or a combination of one or more of them. Moreover,while a computer storage medium is not a propagated signal, a computerstorage medium can be a source or destination of computer programinstructions encoded in an artificially-generated propagated signal. Thecomputer storage medium can also be, or be included in, one or moreseparate components or media (e.g., multiple CDs, disks, or otherstorage devices). Accordingly, the computer storage medium is bothtangible and non-transitory.

The operations described in this specification can be performed by adata processing apparatus on data stored on one or morecomputer-readable storage devices or received from other sources. Theterm “data processing apparatus” or “computing device” encompasses allkinds of apparatus, devices, and machines for processing data, includingby way of example a programmable processor, a computer, a system on achip, or multiple ones, or combinations of the foregoing. The apparatuscan include special purpose logic circuitry, e.g., an FPGA (fieldprogrammable gate array) or an ASIC (application-specific integratedcircuit). The apparatus can also include, in addition to hardware, codethat creates an execution environment for the computer program inquestion, e.g., code that constitutes processor firmware, a protocolstack, a database management system, an operating system, across-platform runtime environment, a virtual machine, or a combinationof one or more of them. The apparatus and execution environment canrealize various different computing model infrastructures, such as webservices, distributed computing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub-programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing actions in accordance with instructions andone or more memory devices for storing instructions and data. Generally,a computer will also include, or be operatively coupled to receive datafrom or transfer data to, or both, one or more mass storage devices forstoring data, e.g., magnetic, magneto-optical disks, or optical disks.However, a computer need not have such devices. Devices suitable forstoring computer program instructions and data include all forms ofnon-volatile memory, media and memory devices, including by way ofexample semiconductor memory devices, e.g., EPROM, EEPROM, and flashmemory devices; magnetic disks, e.g., internal hard disks or removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,special purpose logic circuitry.

It should be noted that the term “example” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

The terms “coupled,” and the like as used herein mean the joining of twomembers directly or indirectly to one another. Such joining may bestationary (e.g., permanent) or moveable (e.g., removable orreleasable). Such joining may be achieved with the two members or thetwo members and any additional intermediate members being integrallyformed as a single unitary body with one another or with the two membersor the two members and any additional intermediate members beingattached to one another.

It is important to note that the construction and arrangement of thevarious exemplary embodiments are illustrative only. Although only a fewembodiments have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter described herein.Additionally, it should be understood that features from one embodimentdisclosed herein may be combined with features of other embodimentsdisclosed herein as one of ordinary skill in the art would understand.Other substitutions, modifications, changes and omissions may also bemade in the design, operating conditions and arrangement of the variousexemplary embodiments without departing from the scope of the presentinvention.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular implementations of particularinventions. Certain features described in this specification in thecontext of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresdescribed in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

What is claimed is:
 1. A system for use with an engine comprising afirst cylinder and a second cylinder, the system comprising: a firstinlet configured to receive air; an intake manifold configured toreceive the air from the first inlet and to provide the air to the firstcylinder and the second cylinder; an exhaust manifold configured toreceive exhaust from the first cylinder and the second cylinder, theexhaust manifold comprising: a first exhaust outlet conduit configuredto receive the exhaust from the first cylinder; and a second exhaustoutlet conduit configured to receive the exhaust from the secondcylinder; a first catalyst disposed along the second exhaust outletconduit and configured to receive the exhaust from the second cylinderand to produce ammonia; and a first recirculation conduit coupled to thefirst exhaust outlet conduit and the intake manifold and configured toselectively provide the exhaust from the first exhaust outlet conduit tothe intake manifold; wherein the second exhaust outlet conduit isisolated from the first exhaust outlet conduit upstream of the firstcatalyst and coupled to the first exhaust outlet conduit downstream ofthe first catalyst.
 2. The system of claim 1, further comprising asecond catalyst disposed along the first exhaust outlet conduit andconfigured to receive the exhaust from the first cylinder and to oxidizethe exhaust; wherein the first exhaust outlet conduit is isolated fromthe second exhaust outlet conduit upstream of the second catalyst andcoupled to the second exhaust outlet conduit downstream of the secondcatalyst.
 3. The system of claim 1, wherein the engine is configuredsuch that, during operation of the engine, the first cylinder isoperated at a first compression ratio and the second cylinder isoperated at a second compression ratio that is different from the firstcompression ratio.
 4. The system of claim 1, further comprising a firstintake throttle; wherein the intake manifold comprises: a first intakemanifold conduit configured to receive the air from the first inlet andto provide the air to the first cylinder; and a second intake manifoldconduit configured to receive the air from the first inlet and toprovide the air to the second cylinder; wherein the first intakethrottle is coupled to the first intake manifold conduit; and whereinthe first intake manifold conduit is coupled to the second intakemanifold conduit upstream of the first intake throttle and isolated fromthe second intake manifold conduit downstream of the first intakethrottle.
 5. The system of claim 4, further comprising a second intakethrottle, the second intake throttle coupled to the second intakemanifold conduit; wherein the second intake manifold conduit is coupledto the first intake manifold conduit upstream of the second intakethrottle and isolated from the first intake manifold conduit downstreamof the second intake throttle.
 6. The system of claim 5, wherein: thefirst intake throttle is configured to provide the air to the firstcylinder at a first flow rate so as to produce a combustible leanair/fuel mixture in the first cylinder; and the second intake throttleis configured to provide the air to the second cylinder at a second flowrate so as to produce a rich air/fuel mixture in the second cylinder. 7.The system of claim 5, further comprising: an intercooler positionedupstream of the intake manifold and configured to receive the air fromthe first inlet at a first temperature and provide the air to the intakemanifold at a second temperature less than the first temperature; aselective catalytic reduction (SCR) system positioned downstream of theexhaust manifold and configured to receive the exhaust from the exhaustmanifold; and a second catalyst disposed along the first exhaust outletconduit and configured to receive the exhaust from the first cylinderand to oxidize the exhaust; and a third catalyst positioned downstreamof the SCR system and configured to receive the exhaust from the SCRsystem and to oxidize the exhaust; wherein the first exhaust outletconduit is isolated from the second exhaust outlet conduit upstream ofthe second catalyst and coupled to the second exhaust outlet conduitdownstream of the second catalyst.
 8. The system of claim 1, furthercomprising a recirculation valve coupled to the first recirculationconduit and configured to cause the first recirculation conduit toprovide the exhaust to the intake manifold.
 9. The system of claim 8,further comprising a cooler positioned along the first recirculationconduit upstream of the recirculation valve and configured to receivethe exhaust from the exhaust manifold at a first temperature and providethe exhaust to the recirculation valve at a second temperature less thanthe first temperature.
 10. The system of claim 1, wherein: the intakemanifold comprises: a first intake manifold conduit configured toreceive the air from the first inlet and to provide the air to the firstcylinder; and a second intake manifold conduit configured to receive theair from the first inlet and to provide the air to the second cylinder;the first intake manifold conduit is coupled to the second intakemanifold conduit; and the first recirculation conduit is coupled to thefirst intake manifold conduit downstream of the second intake manifoldconduit.
 11. The system of claim 10, further comprising a first intakethrottle coupled to the first intake manifold conduit downstream of thesecond intake manifold conduit and upstream of the first recirculationconduit; wherein the first intake throttle is configured to provide theair to the first cylinder at a first flow rate so as to produce acombustible lean air/fuel mixture in the first cylinder.
 12. The systemof claim 1, further comprising: a first compressor configured to receivethe air from the first inlet and to compress the air prior to providingthe air to the intake manifold; and a turbine configured to receive theexhaust from the first exhaust outlet conduit and the exhaust from thesecond exhaust outlet conduit.
 13. The system of claim 12, wherein: theintake manifold comprises: a first intake manifold conduit configured toreceive the air from the first inlet and to provide the air to the firstcylinder; and a second intake manifold conduit configured to receive theair from the first inlet and to provide the air to the second cylinder;and the first recirculation conduit is coupled to the first intakemanifold conduit.
 14. The system of claim 13, further comprising: asecond inlet coupled to the first inlet upstream of the first compressorand configured to receive the air; and a second compressor configured toreceive the air from the second inlet and to compress the air prior toproviding the air to the intake manifold, the second compressoroperatively coupled to the first compressor; wherein the intake manifoldcomprises: a first intake manifold conduit configured to receive the airfrom the first compressor and to provide the air to the first cylinder;and a second intake manifold conduit configured to receive the air fromthe second compressor and to provide the air to the second cylinder. 15.The system of claim 14, further comprising a second recirculationconduit disposed downstream of the turbine and configured to selectivelyprovide the exhaust from the turbine to the first inlet.
 16. Anaftertreatment system for an engine having a first cylinder and a secondcylinder, the aftertreatment system comprising: an exhaust manifoldcomprising: a first exhaust outlet conduit configured to receive exhaustfrom the first cylinder; and a second exhaust outlet conduit configuredto receive exhaust from the second cylinder; a first catalyst disposedalong the second exhaust outlet conduit and configured to receive theexhaust from the second cylinder and to produce ammonia; a secondcatalyst disposed along the first exhaust outlet conduit and configuredto receive the exhaust from the first cylinder and to oxidize theexhaust; a selective catalytic reduction (SCR) system positioneddownstream of the exhaust manifold and configured to receive the exhaustfrom the first catalyst and the second catalyst; a third catalystpositioned downstream of the SCR system and configured to receive theexhaust from the SCR system and to oxidize the exhaust; and a firstrecirculation conduit coupled to the first exhaust outlet conduitupstream of the second catalyst, isolated from the second exhaust outletconduit, and configured to receive the exhaust from the first exhaustoutlet conduit; wherein the first exhaust outlet conduit is isolatedfrom the second exhaust outlet conduit upstream of the second catalyst;wherein the second exhaust outlet conduit is isolated from the firstexhaust outlet conduit upstream of the first catalyst; and wherein thefirst exhaust outlet conduit is coupled to the second exhaust outletconduit downstream of the first catalyst and the second catalyst andupstream of the SCR system.
 17. The aftertreatment system of claim 16,further comprising a second recirculation conduit positioned downstreamof the exhaust manifold and upstream of the SCR system and configured toreceive the exhaust from the first catalyst and the second catalyst. 18.The aftertreatment system of claim 16, further comprising: an ammoniasensor coupled to the second exhaust outlet conduit downstream of thefirst catalyst, the ammonia sensor configured to determine an amount ofammonia in the exhaust provided by the first catalyst; an oxygen sensorcoupled to the second exhaust outlet conduit downstream of the firstcatalyst, the oxygen sensor configured to determine an amount of oxygenin the exhaust provided by the first catalyst; and a NOx sensor coupledto the first exhaust outlet conduit upstream of the second catalyst, theNOx sensor configured to determine an amount of NOx in the exhaustprovided by the first cylinder.
 19. The aftertreatment system of claim16, wherein the exhaust manifold further comprises a third exhaustoutlet conduit configured to receive exhaust from the engine, the thirdexhaust outlet conduit coupled to the first exhaust outlet conduitupstream of the second catalyst and isolated from the second exhaustoutlet conduit upstream of the second catalyst.
 20. A system for usewith an engine having a first cylinder and a second cylinder, the systemcomprising: an inlet configured to receive air; an intake manifoldconfigured to receive the air from the inlet and to provide the air tothe first cylinder and the second cylinder; an exhaust manifoldconfigured to receive exhaust from the first cylinder and the secondcylinder, the exhaust manifold comprising: a first exhaust outletconduit configured to receive the exhaust from the first cylinder; and asecond exhaust outlet conduit configured to receive the exhaust from thesecond cylinder; a catalyst disposed along the second exhaust outletconduit and configured to receive the exhaust from the second cylinderand to produce ammonia; and a recirculation conduit coupled to the firstexhaust outlet conduit and the intake manifold and configured toselectively provide the exhaust from the first cylinder to the intakemanifold; wherein the second exhaust outlet conduit is isolated from thefirst exhaust outlet conduit upstream of the catalyst and coupled to thefirst exhaust outlet conduit downstream of the catalyst; and wherein thesecond exhaust outlet conduit is coupled to the first exhaust outletconduit downstream of the recirculation conduit.
 21. The system of claim20, wherein: the intake manifold comprises: a first intake manifoldconduit configured to provide the air to the first cylinder; and asecond intake manifold conduit configured to provide the air to thesecond cylinder; and the recirculation conduit is coupled to the firstintake manifold conduit.